Europium is a chemical element with the symbol Eu and atomic number 63. Europium is named after the continent Europe. It is the most reactive of the rare earth elements. It rapidly oxidizes in air. Europium ignites in the air at around 302 degrees Fahrenheit. It is quite pliable (bendable). Although it was first discovered by Paul Ã‰mile Lecoq de Boisbaudran in 1890, it is usually credited to French chemist EugÃ¨ne-Anatole DemarÃ§ay, who suspected samples of the discovered samarium...

A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.